ECG

Question 1

What are the three sets of “leads in an ECG?

Answer 1

Limb leads (I, II and III)
Augmented limb leads (aVF, aVL, aVR)
Praecordial leads (V1-V6)

Question 2

In which intercostal space do V1 and V2 electrodes go?

Answer 2

4th IC space

Question 3

Position of:

a) V4
b) V5
c) V6

Answer 3

a) 5th IC, mid clavicular line
b) 5th IC, ant. axillary line
c) 5th IC, mid axillary line

Question 4

What do the limb leads form?

Answer 4

Einthovens triangle

Question 5

Tracing problems in ECG (3)

Answer 5

AC interference
Muscle tremor
Baseline wander

Question 6

Calculation used for rate

Answer 6

300 divided by number of big squares between two R waves

Question 7

How can rate be calculated in patients with tachycardia?

Answer 7

1500 divided by number of small squares between R waves

Question 8

How can rate be calculated when rhythm is irregular?

Answer 8

Count QRS complexes in 30 large squares, multiply by 10

Question 9

What is the cardiac axis?

Answer 9

The “general direction” of depolarization within the heart

Question 10

In a person with normal cardiac axis, which lead is usually a) the most positive and b) the most negative?

Answer 10

a) II (goes in same direction as depolarization)

b) aVR (goes in opposite direction)

Question 11

Axis ranges:

a) normal
b) RAD
c) LAD

Answer 11

a) -30 to 90 degrees
b) 90 to 180 degrees
c) -30 to -90 degrees

Question 12

Axis waveforms:

a) I, II and aVF positive
b) I negative, aVF positive
c) I positive, aVF negative

Answer 12

a) normal
b) RAD
c) LAD

Question 13

Causes of LAD

Answer 13

Expiration
LBBB
Left anterior hemiblock
WPW syndrome

Question 14

Normal PR interval?

Answer 14

120ms-200ms (three to five small squares)

Question 15

What does a prolonged PR interval imply?

Answer 15

1st degree heart block

Question 16

What does a shortened PR interval imply?

Answer 16

Unusually fast conduction via an accessory pathway e.g. WPW syndrome

Question 17

Normal QRS duration

Answer 17

less than 120ms (three small squares)

Question 18

What are the rhymth rules?

Answer 18

1. Is there electrical activity?
2. Is the rhythm regular?
3. What is the heart rate?
4. Are there P waves?
5. What is the relationship between P waves and QRS complexes?
6. What is the QRS duration?